1. Field of the Invention
The present invention relates to a recovery apparatus for an ink jet printer for recording by ejecting ink onto a recording medium.
2. Description of Related Art
A conventionally known ink jet printer includes a recording head for recording by ejecting ink onto a recording medium. The printer also includes a pumping means having a suction cap for contact with a surface of the head on which nozzles are formed. The pumping means can suck ink from the head through the cap in contact with the nozzle formed surface. The printer further includes a control means for controlling the operation of the pumping means. The pumping means is controlled by the control means to perform a suction action. In general, this action develops a high negative pressure for suction to suck ink from the recording head in a dash through the suction cap.
For example, after an ink cartridge is connected to the recording head for the first time, or after the cartridge is replaced with a new one, the ink passage between the head and the cartridge may be filled with air. In such a case, if great suction force is applied through the suction cap, as is the case with a normal purge for recovery from defective ejection during recording operation, to suck ink from the head in a dash, a mixture of ink and air flows rapidly from the cartridge toward and into the head. The rapidly flowing ink bubbles, and consequently the ink in the ejection channels of the head contains air bubbles. In particular, this tendency is remarkable if a filter is fitted between the head and the cartridge to keep foreign substances etc. from moving together with ink toward the head. The filter may cover the ink supply hole of the cartridge. Therefore, for example, after the cartridge is replaced, it is demanded that ink be sucked from the recording head without bubbling as stated above.
On the other hand, when the ejection from the nozzles of the head is defective or bad with dry ink, foreign substances or the like blocking the nozzles, it is preferable that ink be sucked from the head in a dash with high negative pressure.
Automatic suction is performed depending on the length of the nonuse period with a timer fitted in the printer. This suction involves only removing the drying ink from the nozzles with relatively low negative pressure.
As the pump means, U.S. Pat. No. 5,639,220 of the assignee of the present applicant discloses a suction pump having a pump body provided with a suction port and a discharge port which are axially spaced, and a first piston and a second piston slidably fitted in the pump body to form a suction chamber therebetween. In a operation, a driving mechanism of the pump moves the first piston away from the second piston to expand the suction chamber so that negative pressure prevails in the suction chamber and ink is suctioned through the suction port into the suction chamber.